JP5631214B2 - Unsaturated compound purification method and production apparatus - Google Patents

Description

  The present invention relates to a method for purifying unsaturated compounds. In addition, the present invention describes an apparatus for carrying out the method.

  Unsaturated compounds with high boiling points tend to form by-products during purification. This creates various problems in connection with the isolation of the compounds. For example, deposits may form in the generator due to polymerization of unsaturated compounds. Therefore, it is necessary to clean the equipment from time to time to ensure the high quality of the product.

Prior art In addition, the formation of by-products leads to a reduction in the overall yield. These problems can be avoided when refining in a distillation kettle with one column having a slight pressure drop due to less structure. However, this makes it impossible to achieve optimum separation performance. On the other hand, it is necessary in many ways to provide as pure a product as possible. Of particular interest are compounds which are especially glycol esters, such as hydroxyalkyl (meth) acrylates. Besides polymers, these compounds can form di (meth) acrylates, which are particularly undesirable. Efforts have already been made to solve the aforementioned problems.

  For example, the printed document CN1502601 describes a method for purifying a hydroxyalkyl (meth) acrylate having a number of steps. At this time, the individual processes are continuously connected. In the first thin film evaporator, hardly volatile compounds are separated. The evaporated product is condensed and directed to a falling film evaporator. The compound to be purified is purified from readily volatile components in a thin film evaporator. In a further thin film evaporator, this product is removed through the top of the column and the hardly volatile components are returned to the first thin film evaporator in a small product proportion. Correspondingly, the product is not sent to the circulation. Hydroxypropyl (meth) acrylate purified according to the method described in document CN1502601 showed a purity of about 98.7%.

  Further document EP-A-1 090 904 describes a process for the purification of hydroxyalkyl (meth) acrylates. In this method, a distillation kettle is used together with a thin film evaporator, and at this time, the bottom liquid of the distillation kettle is introduced into the thin film evaporator. The column of the still does not have a structure that leads to a pressure drop. This approach yields a purified product with a relatively low purity with a low diester content. However, compared to pure distillation, the purity only increases slightly from 98.1% to 98.5%. What is important here is that the residence time can be kept short. Returning the evaporated product in large quantities from the thin film evaporator to the still is not described quantitatively.

  The method described above has already shown improvements over the prior art. Nonetheless, there is a continuing demand for further improving the purity as well as the yield of unsaturated compounds.

Problem In view of the prior art, the object of the present invention is to provide a process for the purification of unsaturated compounds which leads to a particularly pure product in high yield.

  A further challenge was to establish a method, in particular, with very little by-product formation during purification. In particular, the method was desired to lead to only a small amount of deposits being formed in the purification apparatus. This eliminates the need to interrupt the operation of the device due to the cleaning procedure, and it has been desirable to enable a longer and continuous operation of the device.

  Furthermore, it was desired that the method could be performed as easily and cost-effectively as possible.

  Therefore, a further object of the present invention was to provide an apparatus for carrying out the corresponding method. At this time, it was desired that the apparatus could be cleaned by an easy method.

Solution The problem as well as other explicitly mentioned, but easily derived or inferred from the relations previously discussed introductory, are solved by a method having all the features of claim 1. Appropriate variants of the method according to the invention are protected by the subclaims. For an apparatus for carrying out the method, claim 20 describes a solution to the problem.

Correspondingly, the subject of the present invention is a process for the production of unsaturated compounds, which is purified in an apparatus, the apparatus comprising at least two evaporators, which evaporators contain the unsaturated compounds. some are by Uni connected circulates, this time vapors condensed in the first evaporator is isolated and vapors condensed in the second evaporator to the first evaporator A purification method that is introduced, wherein the mass flow rate for isolating the condensed evaporate from the mixture to be purified in the first evaporator is such that the condensed evaporate is removed from the second evaporator to the first It is characterized by being less than the mass flow rate introduced into the evaporator.

  This can provide a method of the type described above with a particularly good property profile in an unexpected manner. Surprisingly, particularly high purity products are obtained in very good yields.

  Furthermore, by-product formation during purification is particularly minimal. In this case, the method leads to a small amount of deposits being formed in the purification apparatus. As a result, it is not necessary to interrupt the operation of the apparatus, and a longer continuous apparatus operation can be performed.

  In addition, the method according to the invention is very easy and can be carried out cost-effectively.

  Furthermore, the invention provides a device for carrying out the corresponding method, which device can be easily cleaned.

  The method of the present invention is particularly useful for the purification of unsaturated compounds having at least one carbon-carbon double bond. Of particular interest are compounds having a boiling point of about 150 ° C. to about 300 ° C., especially at 1,013 mbar. Suitably the process according to the invention can be used inter alia for the purification of glycol esters. This belongs, for example, to hydroxyethyl (meth) acrylates such as 2-hydroxyalkyl (meth) acrylates, hydroxypropyl (meth) acrylates and isomers, hydroxybutyl (meth) acrylates and isomers, and from the above compounds Is a mixture of The preparation of these compounds is generally known, and the useful indications here are found in particular in the prior art cited above. These compounds can therefore be obtained, inter alia, by reaction of (meth) acrylic acid with epoxides such as ethylene oxide or propylene oxide.

  Purification can be carried out in the presence of stabilizers, in which case these stabilizers can already be used in various ways for the production of unsaturated compounds. Thus, many mixtures to be fractionated already have these compounds, which may optionally be added later. Among the preferred stabilizers are phenol compounds such as hydroquinone, methylhydroquinone, t-butylhydroquinone, 2,6-di-t-butylhydroquinone, 2,5-di-t-butylhydroquinone, 2,4-dimethyl, among others. -6-t-butylphenol and hydroquinone monomethyl ether; p-phenylenediamine, such as N-isopropyl-N'-phenyl-p-phenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-p- Phenylenediamine, N- (1-methylheptyl) -N′-phenyl-p-phenylenediamine, N, N′-diphenyl-p-phenylenediamine, and N, N′-di-2-naphthyl-p-phenylenediamine Amines such as thiodiphenylamine and phenothiazine; copper dialkyl Dithiocarbamates such as copper dibutyldithiocarbamate, copper diethyldithiocarbamate, and copper dimethyldithiocarbamate; nitro compounds such as nitrosodiphenylamine, isoamylnitrite, N-nitrosocyclohexylhydroxylamine, N-nitroso-N-phenyl- N-hydroxylamine and salts thereof; and N-oxyl compounds such as 2,2,4,4-tetramethylazetidine-1-oxyl, 2,2-dimethyl-4,4-dipropylazetidine-1 -Oxyl, 2,2,5,5-tetramethylpyrrolidine-1-oxyl, 2,2,5,5-tetramethyl-3-oxopyrrolidine-1-oxyl, 2,2,6,6-tetramethylpiperidine -1-oxyl, 4-hydroxy-2,2,6,6-tetramethyl Piperidine-1-oxyl, 6-aza-7,7-dimethylspiro [4,5] decan-6-oxyl, 2,2,6,6-tetramethyl-4-acetoxypiperidine-1-oxyl, and 2, 2,6,6-tetramethyl-4-benzoyloxypiperidine-1-oxyl. These compounds may be contained in the mixture to be purified, preferably in an amount ranging from 0.0001% to 1% by weight, particularly preferably from 0.0005% to 0.5% by weight.

This purification is carried out in an apparatus having at least two evaporators. In the scope of the present invention, the term “evaporator” is a suitable device for the transfer of unsaturated compounds to the gas phase. This applies in particular to thin film evaporators, such as falling film evaporators, evaporators with a rotating wipe system, and circulation evaporators, such as forced circulation or natural circulation evaporators. . A short path evaporator (Kurzwegverdampfer) can also be used. Such devices are known (see Ullmanns Encyclopedia of Industhal Chemistry (6. Auflage), Verlag Wiley-VCH, Weinheim 2003, Band 36, page 505).

  In the apparatus for carrying out the process according to the invention, at least two evaporators are connected so that a part of the unsaturated compounds can be sent to one circulation, in which case the first evaporator condenses. The evaporated product is isolated and the condensed product in the second evaporator is introduced into the first evaporator.

As already explained, these evaporators are connected to each other so that a portion of the unsaturated compounds can be sent to one circulation. This means that part of the composition remaining in the first evaporator that has not been transferred to the gas phase is transferred to a second evaporator, for example its bottom. In particular, the column bottom contains a high proportion of hardly volatile compounds. According to the invention, the mass flow rate for isolating the condensed evaporate from the mixture to be purified in the first evaporator is the mass introducing the condensed evaporate from the second evaporator into the first evaporator. Less than the flow rate. Of particular interest is, inter alia, the mass flow rate (3) for isolating the condensed condensate from the mixture to be purified in the first evaporator versus the condensed evaporator from the second evaporator to the first evaporator. The ratio of the mass flow rate (6) introduced into is preferably in the range of 0.4 to 1.5, particularly preferably in the range of 0.5 to 0.8. Thereby, a high proportion of the composition (2) introduced into the first evaporator is introduced into the second evaporator through the tower bottom (4). This ratio is obtained from the ratio of the two mass flow rates mentioned above.

  According to a particular embodiment, the method according to the invention comprises at least three evaporators, with one circulation (4 & 6) between the first and second evaporators, and the second and second One circulation (7 & 9) is formed between the three evaporators, and the above explanation applies accordingly for the circulation.

  At this time, the mass flow rate (6) for introducing the condensed product from the second evaporator into the first evaporator, and the condensed product from the third evaporator to the second evaporator. The mass flow rate (9) ratio may be in the range of 0.75 to 35, particularly preferably in the range of 2 to 10. This configuration of the method according to the invention makes it possible in particular to increase the yield unexpectedly.

  The mixture to be purified can preferably be introduced into the first and / or second evaporator. Of particular interest is a method in which at least part of the mixture to be purified is first introduced into the first evaporator and a further part of the mixture to be purified is first introduced into the second evaporator.

  Suitably, the molar ratio of the portion of the mixture to be purified introduced into the first evaporator to the portion of the mixture to be purified introduced into the second evaporator is from 9: 1 to 0.1: 1. And particularly preferably in the range of 8: 1 to 2: 1.

  The type of evaporator itself is of secondary importance for the implementation of the method according to the invention. However, the use of circulating evaporators as the first and second evaporators has proven appropriate. A thin film evaporator is preferably used as the third evaporator.

  The purification method according to the present invention can be carried out in a wide pressure range and a wide temperature range. In order to keep the formation of by-products as small as possible, the temperature is suitably maintained at a low level. Correspondingly, the process according to the invention is preferably carried out with little pressure. On the other hand, maintaining very little pressure is very expensive.

Thus, particularly suitably, the unsaturated compound is preferably transferred to the gas phase at a pressure in the range from 0.1 mbar to 20 mbar, particularly preferably in the range from 1 mbar to 10 mbar.

The temperature required at this time is obtained from the vapor pressure curve of the unsaturated compound in each case. The temperature at which the unsaturated compound is transferred to the gas phase is generally preferably in the range of 50 to 150 ° C, particularly preferably in the range of 60 ° C to 110 ° C.

According to a particular embodiment of the invention, the first evaporator is preferably operated with a gas load factor of 1.5-2 Pa ^0.5 . Suitably the gas load temperature for operating the first evaporator is preferably in the range of 0.8 to 3.0 Pa ^0.5 . The gas load factor (F factor) is calculated from the product of the gas velocity based on the inner cross-sectional area of the tube for gas discharge and the square root of the gas density (Klaus Sattler, Till Adrian, Thermische Trennverfahren (3. Auflage ), VCH-Verlag, Weinheim 2001, page 234).

  The invention further provides a preferred device for carrying out the method according to the invention. The device according to the invention has at least three evaporators, the residue of the first evaporator remaining in the liquid phase can be directed to the second evaporator, the condensed of the second evaporator Evaporate can be directed to the first evaporator and the residue remaining in the liquid phase of the second still can be directed to the third evaporator, and the condensed evaporator of the third evaporator can be These devices are connected to each other so that they can be directed to the second evaporator.

  According to a particular embodiment of the device of the invention, the device has at least two circulation evaporators and one thin film evaporator. Suitably the mixture to be purified is first led to a circulating evaporator, preferably using a thin film evaporator as the third evaporator.

The evaporant generated in the evaporator can be guided to further components of the device by means of normal connections. In order to discharge the gas after evaporation, a tube is generally used, among other things. Preferably every evaporator has one column, so that the apparatus comprises at least three columns. Here, the word “tower” should be comprehensively understood to include simple tubes. According to a particular embodiment of the invention, towers with a diameter in particular ranging from 0.05 m to 5 m, particularly preferably from 0.3 m to 3 m can be used. In this case, it is appropriate to use, among other things, a column that provides a slight pressure drop effect. Of particular importance is, inter alia, an F factor in the range of 0.8 to 3.0 Pa ^0.5 , preferably in the range of 1.5 to 2.0 Pa ^0.5 , in the range of 0.5 to 10 mbar , preferably in the range of 1 mbar to 5 mbar . This tower leads to a pressure drop. Correspondingly, preferably, a column without packings or structures is used. Excluded here, however, is a mist separator (demister), which helps to keep compounds that do not evaporate under the selected conditions but can be entrained in the mist at the bottom.

Preferably, the composition to be transferred to the gas phase can be condensed (condensed evaporate) before being introduced into the next evaporator. Correspondingly, a cooler may be installed between the different evaporators. Correspondingly, a preferred apparatus for practicing the present invention can include three interconnected stills.

  However, the present invention is not limited to an apparatus having three evaporators or three evaporators. According to a further embodiment, the device according to the invention can have four, five or more than five evaporators, which are correspondingly connected to one another according to the above-mentioned principle. As a result, one circulation is formed between the two evaporators.

  For a more detailed description, the present invention will be described with reference to FIG. 1, but this should not limit the present invention.

  FIG. 1 is a schematic diagram of a preferred apparatus for practicing the present invention. Into the first circulation evaporator (1) is introduced hydroxyalkyl (meth) acrylate obtained from the product through mass flow (2). The circulating evaporator can be operated at a pressure in the range of 1 mbar to 10 mbar, with each ester producing a temperature range of 55 ° C. to 120 ° C. The distillate is condensed and guided from the apparatus through mass flow (3). The coolers necessary for this can form one unit with the evaporator or can be configured as a separate unit. The non-evaporating content of the ester introduced can be directed through the mass stream (4) to the second circulating evaporator (5), where most of the ester fed in this evaporator is evaporated. And after condensation, it is transferred to the first circulation evaporator (1) through the mass stream (6). The residue formed in the second circulation evaporator (5) is guided to the thin film evaporator (8) through the mass flow (7). Similarly, in the thin film evaporator (8), a part of the introduced mixture is transferred to the gas phase, condensed and introduced into the second circulating evaporator (5) through the mass flow (9). The residue remaining in the thin film evaporator (8) is discharged from the apparatus through the mass flow (10).

  The evaporator (5) or (8) can likewise preferably be operated at a pressure in the range of 1 to 10 mbar and at a temperature of 55 to 120 ° C. Preferably, the ratio of the mass flow rate at which the compound to be purified is discharged from the device through mass flow (3) to the mass flow rate at which the hydroxyalkyl (meth) acrylate obtained from the product is introduced into the device through mass flow (2) is , 0.85 to 0.97, preferably 0.90 to 0.95.

  Particularly advantageously, the high-boiling compounds are transported by a conduit (4) to the second circulation evaporator (5) at a high mass flow rate from the first circulation evaporator (1). Mass flow rate transferred from the first circulating evaporator (1) to the second circulating evaporator (5) via the conduit (4) with the high boiling point compound, hydroxyalkyl (meth) acrylate obtained from the product The ratio of the mass flow rates for introducing the water into the device through the conduit (2) is preferably in the range from 0.75 to 2, particularly preferably in the range from 1.20 to 1.80.

  Suitably the mass flow rate for transferring the vapor condensed in the second circulation evaporator (5) to the first circulation evaporator (1) through the conduit (6), the hydroxyalkyl obtained from the product The ratio of the mass flow rate for introducing (meth) acrylate into the apparatus through the conduit (2) is in the range of 0.75 to 1.90, particularly preferably in the range of 1.25 to 1.75, but is limited thereby. Should not be done.

  The residue and high-boiling compound obtained in the second circulation evaporator (5) are introduced into the thin film evaporator (8). Preferably, the high boiling point compound is transferred to the thin film evaporator (8) through the conduit (7), and the hydroxyalkyl (meth) acrylate obtained from the product is supplied through the conduit (2). The apparatus is adjusted so that the ratio of the mass flow rate introduced into is in the range of 0.05 to 1.25, particularly preferably 0.10 to 0.50.

  The gas phase formed in the thin film evaporator (8) is transferred to the second circulation evaporator (5) after condensation. Preferably, the mass flow rate for transferring the condensed evaporate to the second circulating evaporator (5), the mass flow rate for introducing the hydroxyalkyl (meth) acrylate obtained from the product into the apparatus through the conduit (2). Is in the range of 0.01 to 1.20, particularly preferably in the range of 0.05 to 0.50.

  The residue obtained in the thin film evaporator (8) is discharged from the apparatus. Suitably, the ratio of the mass flow rate for discharging the residue obtained in the thin film evaporator (8) from the device to the mass flow rate for introducing the hydroxyalkyl (meth) acrylate obtained from the product into the device through the conduit (2). Is 0.03 to 0.15, particularly preferably 0.05 to 0.10.

  According to FIG. 1, the apparatus was described in the context of hydroxyalkyl (meth) acrylate. The mass flow rate, especially the ratio of individual mass flow rates, applies equally to other unsaturated compounds, especially other glycol esters. The same applies to other types of evaporators or devices containing more than three evaporators. If the mixture to be purified is directed to the device through more than one mass flow rate, the values stated above are relative to the mass flow rate having the total amount introduced into the device.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention should not be limited by this.

1 is a schematic diagram of a preferred apparatus for practicing the present invention.

Example 1
2-Hydroxyethyl methacrylate was purified in a continuous test carried out for 14 days with the apparatus described in FIG. The first circulating evaporator (1) was operated at a pressure of about 2 mbar to 3 mbar and at a temperature of about 66-72 ° C. The feed rate at which 2-hydroxyethyl methacrylate obtained from the previously carried product was introduced into the apparatus via conduit (2) was 1.605 kg / h on average. The mass flow rate of evaporate obtained from the first circulation evaporator (1) from the apparatus through the conduit (3) was 1.518 kg / h on average.

  The residue obtained in the first circulation evaporator (1) was led to the second circulation evaporator (5) through the conduit (4) at an average mass flow of 1.930 kg / h. The second circulating evaporator (5) is operated at a pressure of about 2 mbar to 3 mbar and at a temperature of about 66 ° C. to 74 ° C., where the condensed evaporate averages 1.843 kg / h. The mass flow led to the first circulation evaporator (1) through the conduit (6).

  The residue obtained in the second circulating evaporator (5) was led to the thin film evaporator (8) through the conduit (7) at an average mass flow of 0.580 kg / h. The thin film evaporator (8) is operated at a pressure of about 2 mbar to 3 mbar and at a temperature of about 68 ° C. to 78 ° C., where the condensed evaporate has an average mass flow rate of 0.493 kg / h. It led to the circulation evaporator (5) through the conduit (9). An average of 0.087 kg / h of the resulting residue was discharged from the apparatus through conduit (10).

  The 2-hydroxyethyl methacrylate introduced into the apparatus through conduit (2) had a purity of about 95.0%. The purified 2-hydroxyethyl methacrylate showed a purity of 99.1%. The yield was 94.6%. The device showed no traces of polymer formed after this continued test.

Example 2
Hydroxypropyl methacrylate was purified in a continuous test conducted over 15 days with the apparatus described in FIG. The first circulating evaporator (1) was operated at a pressure of about 2 mbar to 3 mbar and at a temperature of about 68-78 ° C. The feed rate of the hydroxypropyl methacrylate obtained from the previously carried product introduced into the apparatus through conduit (2) was 1.486 kg / h on average. The mass flow rate of evaporate obtained from the first circulation evaporator (1) from the apparatus through the conduit (3) was 1.403 kg / h on average.

  The residue obtained in the first circulation evaporator (1) was led to the second circulation evaporator (5) through the conduit (4) with an average mass flow of 1.540 kg / h.

  The second circulating evaporator (5) is operated at a pressure of about 2 mbar to 3 mbar and at a temperature of about 70 ° C. to 78 ° C., where the condensed evaporate averages 1.475 kg / h. The mass flow led to the first circulation evaporator (1) through the conduit (6).

  The residue obtained in the second circulating evaporator (5) was led to the thin film evaporator (8) through the conduit (7) with an average mass flow of 0.680 kg / h. The thin film evaporator (8) is operated at a pressure of about 2 mbar to 3 mbar and at a temperature of about 72 ° C. to 82 ° C., where the condensed evaporate has an average mass flow of 0.615 kg / h. It led to the circulation evaporator (5) through the conduit (9). An average of 0.065 kg / h of the resulting residue was discharged from the apparatus through conduit (10).

  The hydroxypropyl methacrylate introduced into the apparatus through conduit (2) had a purity of about 95.8%. The purified hydroxypropyl methacrylate showed a purity of 99.1% for the desired product. The yield was 94.4%. The device showed no traces of polymer formed after this continued test.

Example 3
2-Hydroxyethyl acrylate was purified in a continuous test conducted for 11 days with the apparatus described in FIG. The first circulating evaporator (1) was operated at a pressure of about 2 mbar-3 mbar and at a temperature of about 58-68 ° C. The average feed rate of the 2-hydroxyethyl acrylate obtained from the previous product introduced into the apparatus through conduit (2) was 1.330 kg / h. The mass flow rate of the evaporate obtained from the first circulation evaporator (1) led out from the apparatus through the conduit (3) was 1.060 kg / h on average.

  The residue obtained in the first circulation evaporator (1) was led to the second circulation evaporator (5) through the conduit (4) with an average mass flow of 2.100 kg / h. The second circulating evaporator (5) is operated at a pressure of about 2 mbar to 3 mbar and at a temperature of about 60 ° C. to 68 ° C., with the condensed evaporate averaging 1.740 kg / h. The mass flow led to the first circulation evaporator (1) through the conduit (6).

  The residue obtained in the second circulating evaporator (5) was guided to the thin film evaporator (8) through the conduit (7) with an average mass flow of 0.930 kg / h. The thin film evaporator (8) is operated at a pressure of about 2 mbar to 3 mbar and at a temperature of about 62 ° C. to 72 ° C., where the condensed evaporate has an average mass flow rate of 0.660 kg / h. It led to the circulation evaporator (5) through the conduit (9). An average of 0.270 kg / h of the resulting residue was discharged from the apparatus through conduit (10).

  The 2-hydroxyethyl acrylate introduced into the apparatus through conduit (2) had a purity of about 85.3%. The purified 2-hydroxyethyl methacrylate was 99.0% pure. The yield was 79.7%. This device showed very little traces of polymer formed after this continued test.

Comparative Example 1
2-Hydroxyethyl methacrylate was purified in a continuous test conducted over a period of 14 days in an apparatus consisting of one circulation evaporator and one column. The apparatus was operated at a pressure of about 2 mbar-3 mbar and at a temperature of about 65-73 ° C. The average feed rate of the 2-hydroxyethyl methacrylate obtained from the previous product introduced into the center of the column was 1.605 kg / h. The mass flow rate which led the obtained evaporate out of the tower through the tower top was 1.495 kg / h on average. An average of 0.110 kg / h of the resulting residue was discharged from the apparatus from the circulating evaporator.

  The 2-hydroxyethyl methacrylate introduced into the apparatus had a purity of about 95.0%. The purified 2-hydroxyethyl methacrylate showed a purity of 98.5%. The yield was 93.1%.

  The device showed a trace of the polymer formed after this continuous test.

Comparative Example 2
Hydroxypropyl methacrylate was purified in a continuous test conducted over 15 days in an apparatus consisting of one circulation evaporator and one column. The apparatus was operated at a pressure of about 2 mbar-3 mbar and at a temperature of about 67-79 ° C. The feed rate of introducing hydroxypropyl methacrylate obtained from the product carried out earlier into the center of the column was 1.486 kg / h on average. The mass flow rate which led the obtained evaporate out of the tower through the tower top was 1.390 kg / h on average. An average residue of 0.096 kg / h was discharged from the apparatus from the circulation evaporator.

  The hydroxypropyl methacrylate introduced into the apparatus had a purity of about 95.0%. The purified hydroxypropyl methacrylate showed a purity of 98.7%. The yield was 93.5%.

  The device showed a trace of the polymer formed after this continuous test.

Comparative Example 3
2-Hydroxyethyl acrylate was purified in a continuous test conducted over 8 days in an apparatus consisting of one circulation evaporator and one column. The apparatus was operated at a pressure of about 2 mbar-3 mbar and at a temperature of about 56-70 ° C. The average feed rate of the 2-hydroxyethyl acrylate obtained from the previous product introduced into the center of the column was 1.330 kg / h. The mass flow rate from which the obtained evaporated product was led out from the tower through the top of the tower was 0.950 kg / h on average. An average residue of 0.380 kg / h was discharged from the apparatus from the circulating evaporator.

  The 2-hydroxyethyl acrylate introduced into the apparatus had a purity of about 85.3%. The purified 2-hydroxyethyl acrylate showed a purity of 98.5%. The yield was 71.4%. The device had to be stopped after 8 days because too much polymer was formed.

  DESCRIPTION OF SYMBOLS 1 1st evaporator, 2 mass flow, 3 mass flow, 4 mass flow, 5 second evaporator, 6 mass flow, 7 mass flow, 8 3rd evaporator, 9 mass flow, 10 mass flow

Claims (22)

A method for purifying an unsaturated compound for purification in an apparatus, wherein the unsaturated compound is a compound obtained by a reaction between (meth) acrylic acid and an epoxide,
The apparatus has at least three evaporators, with one circulation between the first and second evaporators and one circulation between the second and third evaporators. And these evaporators are connected so that a part of the unsaturated compound circulates, and the evaporate condensed in the first evaporator is isolated and condensed in the second evaporator. In the purification method, the evaporant is introduced into the first evaporator, and the compound obtained by the reaction of the (meth) acrylic acid and the epoxide is transferred from the first evaporator to the second evaporator. ,
The mass flow rate for isolating the condensed evaporate from the mixture to be purified in the first evaporator is less than the mass flow rate for introducing the condensed evaporate from the second evaporator to the first evaporator;
The ratio of the mass flow rate that isolates the evaporate condensed in the first evaporator from the mixture to be purified to the mass flow rate that introduces the condensed evaporate from the second evaporator to the first evaporator is: The said purification method characterized by existing in the range of 0.5-0.8.   The method of claim 1, wherein the unsaturated compound is a glycol ester.   The process according to claim 2, characterized in that the glycol ester is a hydroxyalkyl (meth) acrylate.   The method according to any one of claims 1 to 3, characterized in that the third evaporator is a thin film evaporator.   The ratio of the mass flow rate that introduces the condensed product from the second evaporator into the first evaporator and the mass flow rate that introduces the condensed product from the third evaporator into the second evaporator is: 5. A method according to any one of claims 1 to 4, characterized in that it is in the range of 0.75 to 35.   6. The process according to claim 1, wherein at least part of the mixture to be purified is first introduced into the first evaporator.   7. The process according to claim 1, wherein at least part of the mixture to be purified is first introduced into the second evaporator.   7. At least a part of the mixture to be purified is first introduced into the first evaporator and a further part of the mixture to be purified is first introduced into the second evaporator. 8. The method according to 7.   The amount ratio of a part of the mixture to be purified introduced into the first evaporator to a part of the mixture to be purified introduced into the second evaporator is 9: 1 to 0.1: 1. The method according to claim 8, wherein:   10. A method according to any one of claims 1 to 9, characterized in that the first evaporator is a circulating evaporator.   11. A method according to any one of claims 1 to 10, characterized in that the second evaporator is a circulating evaporator.   12. A method according to any one of the preceding claims, characterized in that the first and / or second evaporator is a forced circulation evaporator.   12. A method according to any one of claims 1 to 11, characterized in that the first and / or second evaporator is a natural circulation evaporator.   14. A process according to any one of claims 1 to 13, characterized in that the starting material is transferred to the gas phase at a pressure in the range of 0.1 mbar to 20 mbar.   15. A process according to any one of claims 1 to 14, characterized in that the unsaturated compound moves into the gas phase at a temperature in the range of 40-120 [deg.] C. The process according to claim 15, characterized in that the gas load factor in the first evaporator is in the range of 0.8 to 3.0 Pa ^0.5 . An apparatus for carrying out the method according to any one of claims 1 to 16, comprising:
The apparatus has at least three evaporators, and the residue of the first evaporator remaining in the liquid phase can be directed to the second evaporator, the condensed evaporator of the second evaporator being Residue remaining in the first evaporator and in the liquid phase of the second evaporator can be directed to the third evaporator, and the condensed evaporator of the third evaporator can be A device characterized in that these evaporators are connected to each other so that they can be directed to the evaporator.   The apparatus according to claim 17, characterized in that the apparatus comprises at least two circulation evaporators and one thin film evaporator.   19. A device according to claim 17 or 18, characterized in that the device has at least three gas discharge towers. 20. The gas discharge tower according to claim 19, characterized in that it has a pressure drop in the range of ^0.5 to 10 mbar with a gas load factor in the range of 0.8 to 3.0 Pa ^0.5 in the first evaporator. Equipment. The apparatus according to claim 19, characterized in that the gas discharge tower has a pressure drop in the range of ^{1 to 5} mbar with a gas load factor in the range of 1.5 to 2.0 Pa ^0.5 in the first evaporator. .   The apparatus according to any one of claims 19 to 21, wherein the gas discharge tower has a mist separator (demister).

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